From 14d097f6418eacf58e300abfb1531111192e9767 Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Fri, 18 Jul 2025 17:19:33 -0700
Subject: [PATCH] Give a message with a span on validation error

---
 compiler/rustc_mir_transform/src/validate.rs   | 18 ++++++++++--------
 .../miri/tests/panic/mir-validation.stderr     | 14 ++++++++++----
 tests/ui/mir/validate/critical-edge.rs         |  4 ++--
 3 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
index cbb9bbfd12f9f..659ca4df159d0 100644
--- a/compiler/rustc_mir_transform/src/validate.rs
+++ b/compiler/rustc_mir_transform/src/validate.rs
@@ -119,14 +119,16 @@ impl<'a, 'tcx> CfgChecker<'a, 'tcx> {
     #[track_caller]
     fn fail(&self, location: Location, msg: impl AsRef<str>) {
         // We might see broken MIR when other errors have already occurred.
-        assert!(
-            self.tcx.dcx().has_errors().is_some(),
-            "broken MIR in {:?} ({}) at {:?}:\n{}",
-            self.body.source.instance,
-            self.when,
-            location,
-            msg.as_ref(),
-        );
+        if self.tcx.dcx().has_errors().is_none() {
+            span_bug!(
+                self.body.source_info(location).span,
+                "broken MIR in {:?} ({}) at {:?}:\n{}",
+                self.body.source.instance,
+                self.when,
+                location,
+                msg.as_ref(),
+            );
+        }
     }
 
     fn check_edge(&mut self, location: Location, bb: BasicBlock, edge_kind: EdgeKind) {
diff --git a/src/tools/miri/tests/panic/mir-validation.stderr b/src/tools/miri/tests/panic/mir-validation.stderr
index dc70d129da3c3..f801ac907e6b8 100644
--- a/src/tools/miri/tests/panic/mir-validation.stderr
+++ b/src/tools/miri/tests/panic/mir-validation.stderr
@@ -1,11 +1,15 @@
+error: internal compiler error: compiler/rustc_mir_transform/src/validate.rs:LL:CC: broken MIR in Item(DefId) (after phase change to runtime-optimized) at bb0[1]:
+                                place (*(_2.0: *mut i32)) has deref as a later projection (it is only permitted as the first projection)
+  --> tests/panic/mir-validation.rs:LL:CC
+   |
+LL |             *(tuple.0) = 1;
+   |             ^^^^^^^^^^^^^^
+
 
 thread 'rustc' panicked at compiler/rustc_mir_transform/src/validate.rs:LL:CC:
-broken MIR in Item(DefId) (after phase change to runtime-optimized) at bb0[1]:
-place (*(_2.0: *mut i32)) has deref as a later projection (it is only permitted as the first projection)
+Box<dyn Any>
 stack backtrace:
 
-error: the compiler unexpectedly panicked. this is a bug.
-
 
 
 
@@ -20,3 +24,5 @@ LL |     extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/mir/validate/critical-edge.rs b/tests/ui/mir/validate/critical-edge.rs
index 2a3bf6a6181b4..7fe3891d6424e 100644
--- a/tests/ui/mir/validate/critical-edge.rs
+++ b/tests/ui/mir/validate/critical-edge.rs
@@ -21,6 +21,8 @@ pub fn f(a: u32) -> u32 {
         }
         bb1 = {
             Call(RET = f(1), ReturnTo(bb2), UnwindTerminate(ReasonAbi))
+//~^ ERROR broken MIR in Item
+//~| ERROR encountered critical edge in `Call` terminator
         }
 
         bb2 = {
@@ -29,5 +31,3 @@ pub fn f(a: u32) -> u32 {
         }
     }
 }
-
-//~? RAW encountered critical edge in `Call` terminator